1. Field of the Invention
The present invention relates to a light guide for guiding light from a light-emitting element for light emission, and a light source apparatus and a reading apparatus using the light guide.
2. Description of the Related Art
In recent years, as a light source of a scanner or a complex machine for reading an image or the like, a light emitting diode (LED) has been used. The use of an LED as a light source can provide a smaller apparatus when compared with a cold cathode fluorescent lighting (Lamp) (CCFL) as in the past (see, for example, Japanese Patent Application Laid-open No. 2008-123766; hereinafter, referred to as Patent Document 1).
In an image reading apparatus including LEDs disclosed in Japanese Patent Application Laid-open No. 2009-80173 (hereinafter, referred to as Patent Document 2), a light guide optical system for guiding the light from the LEDs to a reading surface (platen) has a plurality of optical surfaces cyclically provided in a direction along which the LEDs are arranged. The optical surfaces have power in the direction along which the LEDs are arranged. Thus, nonuniform illuminance is suppressed (see Patent Document 2, paragraph [0031], FIG. 1, for example).